Cutaneous Eruptions as a Consequence of Myeloid Leukemic Infiltration: Differential Diagnosis With a Benign Dermatosis.

Leukemia cutis is an uncommon but clinically significant manifestation of hematologic malignancies caused by infiltration of the skin by malignant leukocytes. Its presentation is highly variable and may closely resemble benign inflammatory dermatoses, frequently leading to diagnostic delay. We report the case of a 76-year-old man with JAK2-positive essential thrombocythemia (ET) who developed persistent, intensely pruritic maculopapular skin lesions initially diagnosed as dermatitis. Despite symptomatic treatment, the lesions progressed and were followed by systemic symptoms. Further investigation revealed acute myeloid leukemia (AML) arising from blastic transformation of ET, with probable cutaneous involvement consistent with leukemia cutis. This case highlights the importance of maintaining a high index of suspicion when evaluating new or treatment-refractory skin lesions in patients with myeloproliferative neoplasms (MPNs), as early recognition may allow timely diagnosis of leukemic transformation and prompt initiation of appropriate therapy.